Topic 8 Electromagnetic Spectrum The light waves that we studied in the last chapter are just one part of a much more extensive range known as electromagnetic waves. All electromagnetic waves have certain fundamental properties in common.

contents  Properties of Electromagnetic Waves  Applications of Electromagnetic Waves  Chapter Review  Properties of Electromagnetic Waves  Applications of Electromagnetic Waves  Chapter Review Resources Read the Textbook! 3.Additional slides and links on online powerpoint slides

electromagnetic spectrum

properties of electromagnetic waves An electromagnetic wave is produced by the simultaneous vibration of electric and magnetic fields. All electromagnetic waves An electromagnetic wave is produced by the simultaneous vibration of electric and magnetic fields. All electromagnetic waves  transfer energy from one place to another  are transverse waves  travel through a vacuum with the same high speed (speed of light) at 3 x 10 8 m s -1  show wave properties like reflection and refraction  transfer energy from one place to another  are transverse waves  travel through a vacuum with the same high speed (speed of light) at 3 x 10 8 m s -1  show wave properties like reflection and refraction

properties of electromagnetic waves All electromagnetic waves obey the wave equation. v = f V = speed of wave(m/s) f =frequency of wave (Hz) =wavelength of wave (m) V = speed of wave(m/s) f =frequency of wave (Hz) =wavelength of wave (m)

Components of electromagnetic spectrum Speed in a vacuum is constant c = 3 x 10 8 m s -1 Electromagnetic Spectrum Gamma rays X-raysUltraviolet Visible light InfraredMicrowave Radio wave low frequency high frequency short wavelength long wavelength Several km < m electromagnetic spectrum applications of electromagnetic waves

radio wave applications of electromagnetic waves  is the longest EM wave in the electromagnetic spectrum  has wavelength of to 10 5 m  is used in radio communication (LW, MW, SW and VHF) and television transmission (UHF and VHF) over long distances  is the longest EM wave in the electromagnetic spectrum  has wavelength of to 10 5 m  is used in radio communication (LW, MW, SW and VHF) and television transmission (UHF and VHF) over long distances television transmission is made possible with the use of VHF and UHF radio waves  source: TV and radio transmitters detector: aerials of TV and radio receivers  source: TV and radio transmitters detector: aerials of TV and radio receivers

microwave applications of electromagnetic waves  is very similar to UHF radio waves  has wavelength of to m  is used in satellite communication and transmission, radar systems and microwave cooking  travels in straight line without losing much of its energy  is very similar to UHF radio waves  has wavelength of to m  is used in satellite communication and transmission, radar systems and microwave cooking  travels in straight line without losing much of its energy  source: electronic devices (klystron tubes)  detector: microwave receivers  source: electronic devices (klystron tubes)  detector: microwave receivers speed-monitoring radar satellite station Click on internet resource: Youtube video Danger of boiling water using microwaves Youtube video

infra-red radiation applications of electromagnetic waves  is the radiation beyond the red end of the visible spectrum  has wavelength of to m  is used in remote control devices, intruder alarms, infra- red photography and radiant heaters  is the radiation beyond the red end of the visible spectrum  has wavelength of to m  is used in remote control devices, intruder alarms, infra- red photography and radiant heaters  is emitted by objects with temperature above 0 K; hotter objects more than colder ones  source: warm bodies detector: special photographic films, blackened thermometers and thermocouples  is emitted by objects with temperature above 0 K; hotter objects more than colder ones  source: warm bodies detector: special photographic films, blackened thermometers and thermocouples an IR photograph

visible light applications of electromagnetic waves  can be seen by human eye  has wavelength of 4 x to 7 x m  can be seen by human eye  has wavelength of 4 x to 7 x m  is used in optical fibres, medical usage, telecommunications, chemical spectral analysis and photosynthesis  source: hot bodies, lasers and sun detector: eyes, photographic film and photocells  is used in optical fibres, medical usage, telecommunications, chemical spectral analysis and photosynthesis  source: hot bodies, lasers and sun detector: eyes, photographic film and photocells laser surgery

ultra-violet radiation applications of electromagnetic waves  is the radiation beyond the violet end of the visible spectrum  has wavelength of to m  stimulates our bodies to produce vitamin D  is the radiation beyond the violet end of the visible spectrum  has wavelength of to m  stimulates our bodies to produce vitamin D  is used in sunbeds, fluorescent tubes, sterilisation, forgery detection and fluorescence in washing powders  source: sun, mercury vapour and lamps  detector: photographic film, fluorescent screens, dyes and photocells  is used in sunbeds, fluorescent tubes, sterilisation, forgery detection and fluorescence in washing powders  source: sun, mercury vapour and lamps  detector: photographic film, fluorescent screens, dyes and photocells Over exposure to UV radiation can cause skin cancer

x-ray applications of electromagnetic waves  has wavelength of to m  is penetrating and can cause damage to tissues and organisms  is used in medical and dental diagnostic tools and engineering applications  source: x-ray tubes detector: photographic film and fluorescent screens  has wavelength of to m  is penetrating and can cause damage to tissues and organisms  is used in medical and dental diagnostic tools and engineering applications  source: x-ray tubes detector: photographic film and fluorescent screens x-ray photograph of hand

gamma ray applications of electromagnetic waves  has wavelength of to m  is penetrating and can cause damage to living tissues and organisms  is used in medical treatment and checking of welds, under controlled situations  source: cosmic rays, radioactive substances and nuclear reaction detector: Geiger-Müller counters, bubble/cloud chambers and photographic film  has wavelength of to m  is penetrating and can cause damage to living tissues and organisms  is used in medical treatment and checking of welds, under controlled situations  source: cosmic rays, radioactive substances and nuclear reaction detector: Geiger-Müller counters, bubble/cloud chambers and photographic film Click on internet resource: Civil Defence Emergency HandbookCivil Defence Emergency Handbook, read pages 59 to 61

How does our Galaxy look like? Milky Way

1. How many types of electromagnetic waves are associated with a handphone? 2. What other types of waves are associated with a handphone? 4 types: radio waves (FM radio reception) microwaves (transmit signals) visible light (screen display) infra-red waves (IR transmission between handphones) Sound waves (which are not electromagnetic waves)

Electromagnetic waves c = 3 x 10 8 m s -1 Transverse waves are with speed in vacuum consist of Components Radio waves Microwaves Infra-red waves Infra-red waves. Light Light. Ultra-violet Ultra-violet. X-rays X-rays. Gamma rays Applications Radio and television communication Satellite television and telephone Home electrical appliances, remote controls and intruder alarms Optical fibres in medical usage and telecommuncation Sunbeds, fluorescent tubes and sterilisation Medical use and engineering applications Medical treatment